This invention relates generally to broadband communications, and more specifically, the invention relates to a method, system, and apparatus for implementing RF power measurements in a broadband communications device, such as a DOCSIS compliant cable modem. The invention is applicable to at least those broadband devices comprising the LBTXXXXPHY chip family.
The newer DOCSIS standards, such as ECO, recommend that Broadband Communication Devices (BCDs) have the ability to measure the power of an input RF signal. Particularly, this feature recommended in DOCSIS 1.0 and requires this feature in DOCKS 1.1. Measurement accuracy should be within 3 dBmV of real input power. Controller Modules (CMs) which incorporate a low cost single conversion tuner in their front-end solution suffer from a relatively large gain variance as the temperature and frequency change. In fact, the overall gain variance may be as large as +/xe2x88x9210 dB. This makes power measurement difficult.
One Broadband Communication device, the LBT403OPHY, uses a Take Over Point (TOP) scheme for controlling AGC circuits in a CM. The invention provides solutions that enable accurate power measurement in a BCD, using the qualities of the TOP scheme.
The invention provides technical advantages as systems, methods, and devices that compensate for temperature, frequency, and sampling effects in a broadband communication device""s power measurements. One embodiment of a system includes a thermal device, and an automatic gain control circuit coupled to the thermal device such that the thermal device is enabled to compensate for variances in the automatic gain control circuit.
In another embodiment, the method includes the acts of disabling a TOP operation, setting a RF input power, reading an AGC GAIN value, and setting the broadband communications device based on the read AGC value. Furthermore, a broadband communications device according to the invention may operate by disabling a TOP operation, setting a RF input power, reading an AGC GAIN value, and setting the broadband communications device based on the read AGC value.